1. Field of the Invention
The invention relates to multi-phase electrical switch apparatus and, more particularly, to apparatus utilizing multi-phase electrical switches for providing phase reversal of associated multi-phase electrical circuits.
2. Description of the Prior Art
Certain applications in the generation, transmission, distribution, and utilization of electrical energy require the reversal of phases of a multi-phase electrical circuit. For example, pumped-storage electrical generation projects utilize a dual mode dynamoelectric machine in the motor mode to pump water into a reservoir to increase the head behind a dam. This pumping occurs during off-peak hours when the total load on the utiliy grid is low. When the demand for electrical energy on the grid increases, the reservoir is drained to drive the dynamoelectric machine in the generator mode to produce electric power which is supplied to the grid. The transformation between motor mode and generator mode is accomplished by reversing the phase connections to the machine. To provide this phase reversal in a three-phase system generally requires a five-pole switch and a mechanism for operating the poles in the proper sequence.
Such a mechanism must meet a variety of requirements. The mechanism must be adaptable to accommodate variations in the phase-to-phase spacing encountered in various mounting configurations and it should be positively linked o all switches at all times and at all positions of travel of the switches from the fully opened position to the fully closed position. This is to prevent accidental opening or closing of the switches due to vibrations or gravity. During the phase-reversal cycle, one of the switches must open fully and reclose fully. Furthermore, all five switches should be completely open at the mid-point of the phase reversal cycle; that is, no switches should be opening while the others are closing. It is desirable to provide a mechanism which meets these requirements in an efficient, economical manner.